1. Field of the Invention
The present invention relates to power supplies for computer systems, and more specifically to improving power efficiency for different sized loads.
2. Background of the Related Art
A computer system is powered by an electrical power supply that converts electricity from an electrical power source, such as an AC (alternating current) power outlet, to a form usable by a computer system and its various components. For example, a power supply may convert AC to DC (direct current) to supply electrical power at one or more desired DC amperage and voltage. One or more redundant power supplies are sometimes included to provide a backup in the event of a failure of a primary power supply.
The power requirements of computer systems vary widely among the multitude of different computer systems available in the marketplace. For example, the power requirement of a computer system may depend in part on the type of computer system, such as a desktop computer, portable computer, server, or rack-mount system. The power requirement of a computer system may also depend on the particular model or series of the computer system. Even within a particular series or model of computer system, the power requirement of a computer system may further depend on the specific hardware configuration or choice of software applications chosen by an end user. The type, series or model, and the individual hardware/software configuration of a computer system may determine power-related parameters of a computer system, such as the idle power, nominal power, maximum power, and the amount of time spent in a particular power or load range.
The efficiency of a power supply is a significant factor in the cost and environmental impact of operating a computer system. Furthermore, the efficiency of a power supply will typically vary according to the load on the power supply. A particular power supply may be designed and built, however, to be most efficient when operating in a target power range. Although the efficiency of a power supply is always less than 100%, a power supply may have a very good efficiency, such as on the order of 90% or better, when operated under the load or range of loads for which the power supply is optimized.